Junos Cup 2014
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Junos Cup 2014

Tournament 4: Belgium Challenge & Solution: BGP Multicast VPN

[ Edited ]
‎07-03-2014 07:01 AM

Country Flag: Belgium

 

Author: Victor Rodriguez

 

Title: BGP Multicast VPN

 

Type: Service Provider

 

Difficulty: Medium (1 point)

 

Technical Description: Using just one configuration set command, fix the scenario in such a way that the multicast flow reaches the receiver.

Belgium-Topology

 

Challenge Instructions:

For this challenge, you need to start the topology called: “BELGIUM – BGP Multicast VPN”.

 

This challenge shows a VPN named vpn1. CE2 is the source for the multicast group 239.22.22.22, while CE1 is a receiver for that multicast group.

 

You need to launch a ping in CE2 to generate the multicast traffic. Execute on a session connected to CE2:

juniper@CE2> ping 239.22.22.22 interface ge-0/0/1 bypass-routing ttl 20

 

You won’t get a response. Let the ping run while you are troubleshooting this challenge. Once you have succeeded you will get a response to the above ping.

 

You need to fix the problem with just one set command on a single router similar to the following:

configure

set <command>

commit and-quit

 

To solve this challenge submit a brief explanation of the problem and the single-command fix.

 

 

NOTE: If you have issues connecting to the Junosphere topology please check Junosphere Technical documentation, or request assistance in the Junosphere forum 

 

OFFICIAL SOLUTION:

 

PE2 receives the (10.22.22.22, 239.22.22.22) flow, but it doesn’t advertise it via BGP because PE2 is not the DR at the access network ge-0/0/1:

 

juniper@PE2> show pim interfaces instance vpn1 ge-0/0/1

 

Stat = Status, V = Version, NbrCnt = Neighbor Count,

S = Sparse, D = Dense, B = Bidirectional,

DR = Designated Router, P2P = Point-to-point link,

Active = Bidirectional is active, NotCap = Not Bidirectional Capable

 

Name        Stat Mode IP V State       NbrCnt JoinCnt(sg/*g) DR address

ge-0/0/1.0  Up   S     4 2 NotDR,NotCap     1 0/0            10.22.22.22

 

 

We fix if by forcing PE2 to become the DR on the access segment:

 

juniper@PE2# set routing-instances vpn1 protocols pim interface ge-0/0/1.0 priority 100   

 

 

juniper@PE2> show pim interfaces instance vpn1 ge-0/0/1

 

Stat = Status, V = Version, NbrCnt = Neighbor Count,

S = Sparse, D = Dense, B = Bidirectional,

DR = Designated Router, P2P = Point-to-point link,

Active = Bidirectional is active, NotCap = Not Bidirectional Capable

 

Name        Stat Mode IP V State       NbrCnt JoinCnt(sg/*g) DR address

ge-0/0/1.0  Up   S     4 2 DR,NotCap        1 0/0            10.22.22.2

 

 

As a result, PE2 advertises a “Source Active” BGP route:

 

juniper@PE2> show route advertising-protocol bgp 172.16.255.1 table vpn1.mvpn

 

vpn1.mvpn.0: 4 destinations, 5 routes (4 active, 0 holddown, 0 hidden)

  Prefix            Nexthop          MED     Lclpref    AS path

  1:100:1:172.16.255.2/240                  

*                         Self                         100        I

  5:100:1:32:10.22.22.22:32:239.22.22.22/240                  

*                         Self                         100        I

 

And the ping command at CE2 starts getting replies.

Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider